You don't actually need to go through version 3 first - you can download the latest version and let it update your database directly. But because the update from version 2 to version 3 was a paid one, you do need new serial numbers for version 4 because it won't accept your old serial numbers.
To purchase a new serial number, go to our update page http://www.bruji.com/update.html, enter your email address and hit the appropriate button. (Depending on the program you want to update or 'All Three' if it's all three Pedia programs.) That'll take you to our store with the cart pre-filled and the update coupon applied.
After you have received your new serial number(s), you can run the latest version of the Pedias and the programs will do the database update for you. (You'll see it do that the first time you run the programs. This should not take longer than a minute.)
If the update of the files takes longer than that and it seems to be stuck, please get in touch with us.